/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.primitives.Primitives;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import java.util.Spliterator;

/**
 * A mutable class-to-instance map backed by an arbitrary user-provided map. See also
 * {@link ImmutableClassToInstanceMap}.
 *
 * <p>
 * See the Guava User Guide article on
 * <a href= "https://github.com/google/guava/wiki/NewCollectionTypesExplained#classtoinstancemap">
 * {@code
 * ClassToInstanceMap}</a>.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtIncompatible
@SuppressWarnings("serial") // using writeReplace instead of standard serialization
public final class MutableClassToInstanceMap<B> extends ForwardingMap<Class<? extends B>, B>
        implements ClassToInstanceMap<B>, Serializable {

    /**
     * Returns a new {@code MutableClassToInstanceMap} instance backed by a {@link HashMap} using
     * the default initial capacity and load factor.
     */
    public static <B> MutableClassToInstanceMap<B> create() {
        return new MutableClassToInstanceMap<B>(new HashMap<Class<? extends B>, B>());
    }

    /**
     * Returns a new {@code MutableClassToInstanceMap} instance backed by a given empty
     * {@code backingMap}. The caller surrenders control of the backing map, and thus should not
     * allow any direct references to it to remain accessible.
     */
    public static <B> MutableClassToInstanceMap<B> create(Map<Class<? extends B>, B> backingMap) {
        return new MutableClassToInstanceMap<B>(backingMap);
    }

    private final Map<Class<? extends B>, B> delegate;

    private MutableClassToInstanceMap(Map<Class<? extends B>, B> delegate) {
        this.delegate = checkNotNull(delegate);
    }

    @Override
    protected Map<Class<? extends B>, B> delegate() {
        return delegate;
    }

    /**
     * Wraps the {@code setValue} implementation of an {@code Entry} to enforce the class
     * constraint.
     */
    private static <B> Entry<Class<? extends B>, B> checkedEntry(final Entry<Class<? extends B>, B> entry) {
        return new ForwardingMapEntry<Class<? extends B>, B>() {
            @Override
            protected Entry<Class<? extends B>, B> delegate() {
                return entry;
            }

            @Override
            public B setValue(B value) {
                return super.setValue(cast(getKey(), value));
            }
        };
    }

    @Override
    public Set<Entry<Class<? extends B>, B>> entrySet() {
        return new ForwardingSet<Entry<Class<? extends B>, B>>() {

            @Override
            protected Set<Entry<Class<? extends B>, B>> delegate() {
                return MutableClassToInstanceMap.this.delegate().entrySet();
            }

            @Override
            public Spliterator<Entry<Class<? extends B>, B>> spliterator() {
                return CollectSpliterators.map(delegate().spliterator(), MutableClassToInstanceMap::checkedEntry);
            }

            @Override
            public Iterator<Entry<Class<? extends B>, B>> iterator() {
                return new TransformedIterator<Entry<Class<? extends B>, B>, Entry<Class<? extends B>, B>>(
                        delegate().iterator()) {
                    @Override
                    Entry<Class<? extends B>, B> transform(Entry<Class<? extends B>, B> from) {
                        return checkedEntry(from);
                    }
                };
            }

            @Override
            public Object[] toArray() {
                return standardToArray();
            }

            @Override
            public <T> T[] toArray(T[] array) {
                return standardToArray(array);
            }
        };
    }

    @Override
    @CanIgnoreReturnValue
    public B put(Class<? extends B> key, B value) {
        return super.put(key, cast(key, value));
    }

    @Override
    public void putAll(Map<? extends Class<? extends B>, ? extends B> map) {
        Map<Class<? extends B>, B> copy = new LinkedHashMap<Class<? extends B>, B>(map);
        for (Entry<? extends Class<? extends B>, B> entry : copy.entrySet()) {
            cast(entry.getKey(), entry.getValue());
        }
        super.putAll(copy);
    }

    @CanIgnoreReturnValue
    @Override
    public <T extends B> T putInstance(Class<T> type, T value) {
        return cast(type, put(type, value));
    }

    @Override
    public <T extends B> T getInstance(Class<T> type) {
        return cast(type, get(type));
    }

    @CanIgnoreReturnValue
    private static <B, T extends B> T cast(Class<T> type, B value) {
        return Primitives.wrap(type).cast(value);
    }

    private Object writeReplace() {
        return new SerializedForm(delegate());
    }

    /**
     * Serialized form of the map, to avoid serializing the constraint.
     */
    private static final class SerializedForm<B> implements Serializable {
        private final Map<Class<? extends B>, B> backingMap;

        SerializedForm(Map<Class<? extends B>, B> backingMap) {
            this.backingMap = backingMap;
        }

        Object readResolve() {
            return create(backingMap);
        }

        private static final long serialVersionUID = 0;
    }
}
